Thin film head, producing method thereof and magnetic disk apparatus

ABSTRACT

A lower magnetic pole front end portion is provided on a lower magnetic pole main layer, and then, an upper magnetic pole front end portion or an upper magnetic pole front end layer is formed on the flat surface so as to enhance the track width accuracy of thin film head. The height of the lower magnetic pole front end portion is increased so as to enhance the magnetic field intensity. A projection step portion having a width larger than that of the upper magnetic pole front end layer is provided on the lower magnetic pole front end portion. The unnecessary medium in-plane magnetic field can be thus reduced in the off-track position. The respective parts of the head are corrected, thereby realizing a high recording magnetic field intensity exceeding 716 kA/m (9000 Oe).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thin film head for use in amagnetic disk apparatus, particularly, to a thin film head for highcoercivity media suitable for high density recording, a producing methodthereof, and a magnetic disk apparatus.

[0003] 2. Description of Background

[0004] In recent years, as the recording density of magnetic diskapparatuses has been increased, there has been strongly requireddevelopment of thin film heads excellent in read/write characteristicstogether with improvement of the performance of recording media. Atpresent, as a reading head, there is used a head using a MR(magnetoresistive effect) element or a GMR (giant magnetoresistiveeffect) element capable of providing high read output. Further, a TMR(tunnel magnetoresistive) element capable of providing a higher readingefficiency is developed. On the other hand, as a recording head, a priorart inductive thin film recording head using electromagnetic inductionis used. A read/write type thin film head integrally forming the readinghead and the recording head is employed.

[0005] To improve the recording characteristics of a thin film head, astrong and steep recording magnetic field must be generated in order tosufficiently record on recording media having a high coercivity. Thetrack width is reduced with increasing of the track density. Magneticsaturation is caused at the magnetic pole front end portion of the thinfilm head so as to decrease the recording magnetic field. To cope withincreasing of the track density, the processing accuracy of the smalltrack width must be increased.

[0006] As shown in FIG. 3, a prior art thin film head has a substrate 1made of a non-magnetic material. A lower magnetic shield 2 made of asoft magnetic material for enhancing the reading resolution to eliminatethe influence of the external magnetic field is provided thereon. Areading gap 3 made of a nonmagnetic insulating material is providedthereon. A reading element 4 consisting of an MR or GMR element isdisposed in the reading gap. A lower magnetic pole 5 made of a softmagnetic material serving as an upper magnetic shield is providedthereon. A recording gap layer 6 and a coil insulating layer 7 areprovided thereon. Lower layer coils 8 and upper layer coils 8′ aredisposed in the coil insulating layer. There may be a case of only onecoil layer. An upper magnetic pole 9 made of a high saturation magneticflux density material is provided. The entire head is protected by aprotective layer 10. A rear end portion of upper magnetic pole 11 iscontacted magnetically with the lower magnetic pole 5 through a throughhole of the insulating layer 7 and the recording gap layer 6. The widthof a front end portion of upper magnetic pole 12 in a floating surface13 is processed into a width corresponding to the track width. The coils8 and 8′ are constructed so as to be arranged circumferentially aboutthe rear end portion of upper magnetic pole.

[0007] A recording electric current is applied to the coils 8 and 8′ soas to induce a magnetic flux in the upper magnetic pole 9 and the lowermagnetic pole 5. A recording magnetic field generated from the front endof the recording gap records a signal onto a recording medium 14 movingslightly away from the floating surface 13. The magnetic flux isconcentrated in the vicinity of the recording gap from the lowermagnetic pole and the upper magnetic pole. As a result, a high magneticfield is generated. The length in the front end portion of uppermagnetic pole is contacted with the recording gap layer 6 is called agap depth Gd. As the length is reduced, the recording magnetic field isincreased since the magnetic flux is concentrated onto the magnetic polefront end.

[0008] When the upper magnetic pole 9 is formed, a photoresist is coatedonto the coil insulating layer 7 and the recording gap layer 6. Thephotoresist is exposed and developed through a predetermined mask of theshape of the upper magnetic pole so as to remove the photoresist in aportion to be the shape of the upper magnetic pole. A high saturationmagnetic flux density material as the upper magnetic pole is formed inthe removed portion by a plating method.-In the prior art thin filmhead, as described above, the photoresist for forming the upper magneticpole is formed on a high and steep slope 15 of the coil insulating layer7. When the photoresist is exposed, the shape of the upper magnetic polecannot be formed accurately due to light reflection from the slope andinsufficient depth of focus. In particular, a problem arises when asmall track width of the rear end portion of upper magnetic pole isformed.

[0009] As a method for solving this point, as described in JapanesePublished Unexamined Patent Application No. 2000-276707, there isproposed a method for separating an upper magnetic pole into an uppermagnetic pole front end layer, an upper magnetic pole rear end layer,and an upper magnetic pole top layer. In this method, as shown in FIG.4, a recording gap layer 6 is formed, and then, a first non-magneticinsulating layer 16 for defining a gap depth. A photoresist for formingan upper magnetic pole front end layer 17 and an upper magnetic polerear end layer 18 is formed thereon. The photoresist is exposed anddeveloped to remove portions to be the shapes of the upper magnetic polefront end layer 17 and the upper magnetic pole rear end layer 18. A highsaturation magnetic flux density material as the upper magnetic polefront end layer 17 and the upper magnetic pole rear end layer 18 isformed in the removed portions by a plating method. Further, the gapbetween the upper magnetic pole front end layer 17 and the uppermagnetic pole rear end layer 18 is buried by a second nonmagneticinsulating layer 19. The upper magnetic pole front end layer 17, theupper magnetic pole rear end layer 18, and the second non-magneticinsulating layer 19 are flattened by polishing. A coil insulating layer7, lower layer coils 8, upper layer coils 8′, an upper magnetic pole toplayer 20, and a protective layer 10 are formed thereon. In this method,the photoresist for forming the upper magnetic pole front end layer 17is formed on the first non-magnetic insulating layer 16 having a stepsmaller than that of the slope 15 of the coil insulating layer in theprior art shown in FIG. 3. The problems of light reflection from thesubstrate or insufficient depth of focus can be eliminated so as toenhance the small track width processing accuracy.

[0010] In the thin film head shown in FIG. 4, the upper magnetic polefront end layer 17 is formed on the step of the first non-magneticinsulating layer 16. A very small track width of 0.4 μm or less whichhas been required in recent years is difficult to be formed at highaccuracy.

[0011] As the track is smaller and the coercivity of the media ishigher, the recording magnetic field required for the recording head isincreased more and more.

SUMMARY OF THE INVENTION

[0012] The present invention solves these difficulties and an object ofthe present invention is to provide a thin film head permitting highdensity recording and reading, a producing method thereof, and amagnetic disk apparatus using such a thin film head.

[0013] To achieve the foregoing object, in the present invention, a thinfilm head comprising in combination: a reading part consisting of amagnetic shield layer and a reading element formed on a substrate; and arecording part consisting of a lower magnetic pole, an upper magneticpole, coils, and a non-magnetic insulating layer; wherein the lowermagnetic pole consists of a lower magnetic pole main layer, a lowermagnetic pole front end portion, and a lower magnetic pole rear endportion; the upper magnetic pole has its front end portion opposite tothe lower magnetic pole front end portion through a recording gap layerand its rear end portion connected magnetically to the lower magneticpole rear end portion; the coils are disposed between the lower magneticpole main layer and the upper magnetic pole; the non-magnetic insulatinglayer is filled between the coils, the lower magnetic pole main layerand the upper magnetic pole; the lower magnetic pole front end portionhas a width in the track width direction smaller than the width of thelower magnetic pole main layer and has, at the upper magnetic pole side,a projection step portion having a width in a floating surface almostequal to the track width; the upper magnetic pole consists of an uppermagnetic pole front end layer, an upper magnetic pole rear end layer,and an upper magnetic pole top layer; and a surface for defining a gapdepth of the lower magnetic pole front end portion is formed almostperpendicular to the recording gap surface, so that the height of thelower magnetic pole front end portion in the medium running direction is0.3 μm to 2 μm.

[0014] The width of the lower magnetic pole front end portion in thetrack width direction is desirably 1 μm to 30 μm.

[0015] The surface other than the projection step portion of the lowermagnetic pole front end portion at the upper magnetic pole side isinclined at, at least one inclination angle to the recording gapsurface.

[0016] The lower magnetic pole front end portion has a width in thetrack width direction smaller than the width of the lower magnetic polemain layer and has, at the upper magnetic pole side, a projection stepportion having a width in a floating surface almost equal to the trackwidth, and having a width in the position away from the floating surfacein the head rear portion direction larger than that of the uppermagnetic pole; and a surface for defining a recording gap depth of thelower magnetic pole front end portion is formed almost perpendicular tothe recording gap surface.

[0017] The upper magnetic pole front end layer has a width correspondingto the track width from the floating surface to the magnetic poleexpansion position, so as to increase the width from the magnetic poleexpansion position to the head rear portion direction.

[0018] The upper magnetic pole front end layer consists of a pluralityof magnetic layers having different saturation magnetic flux densities,so that the magnetic layer of the recording gap side has a saturationmagnetic flux density higher than that of the magnetic layer at a sidefarther from the recording gap.

[0019] The saturation magnetic flux density of at least some magneticmaterials for use in the upper magnetic pole front end layer or thelower magnetic pole front end portion is desirably higher than that ofthe magnetic material for use in the lower magnetic pole main layer andthe upper magnetic pole top layer.

[0020] The specific resistance of the magnetic material for use in thelower magnetic pole main layer or the upper magnetic pole top layer isdesirably higher than that of the magnetic material for use in the uppermagnetic pole front end layer or the lower magnetic pole front endportion.

[0021] The lower magnetic pole front end portion is produced on thelower magnetic pole main layer by a frame plating method.

[0022] A magnetic disk apparatus comprises: a magnetic recording medium;a motor for driving the same; a magnetic head for recording andreproduction onto the magnetic recording medium; a mechanism forpositioning the magnetic head, a circuit system for controlling these;and a circuit system for supplying a recording signal to the magnetichead and processing a reading signal from the magnetic head; wherein atleast the one thin film head is mounted as the magnetic head, and themagnetic recording medium having a coercivity of 279 kA/m (3500 Oe) ormore is used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a perspective view of a thin film head of the presentinvention;

[0024]FIG. 2 is a cross-sectional view of the thin film head of thepresent invention;

[0025]FIG. 3 is a cross-sectional view showing one example of a priorart thin film head;

[0026]FIG. 4 is a cross-sectional view showing another example of theprior art thin film head;

[0027]FIG. 5 is a perspective view showing the shape of a lower magneticpole front end portion on a lower main layer of the thin film head ofthe present invention;

[0028]FIG. 6 is a plan view showing the shape of an upper magnetic polefront end layer of the thin film head of the present invention;

[0029]FIG. 7 is a perspective view showing the shape of a projectionstep portion provided on a lower magnetic pole front end portion on alower magnetic pole main layer of another embodiment of the thin filmhead of the present invention as well as the shape of an upper magneticpole front end portion;

[0030]FIG. 8 is a perspective view showing the shape of a projectionstep portion provided on a lower magnetic pole front end portion on alower magnetic pole main layer of a further embodiment of the thin filmhead of the present invention as well as the shape of an upper magneticpole front end portion;

[0031]FIG. 9 is a cross-sectional view of another embodiment of the thinfilm head of the present invention;

[0032]FIG. 10 is a cross-sectional view of a further embodiment of thethin film head of the present invention;

[0033]FIG. 11 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the height Lp2h of the lower magneticpole front end portion of the thin film head of the present invention;

[0034]FIG. 12 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the width Lp2w of a lower magneticpole front end portion in the track width direction of the thin filmhead of the present invention;

[0035]FIG. 13 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the gap depth Gd of the thin filmhead of the present invention;

[0036]FIG. 14 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the trim depth of the thin film headof the present invention;

[0037]FIG. 15 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the taper angle, i.e., theinclination angle α of the upper end surface of the lower magnetic polefront end portion of the thin film head of the present invention;

[0038]FIG. 16 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the magnetic pole expansion positionLy of an upper magnetic pole front end layer of the thin film head ofthe present invention;

[0039]FIG. 17 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the magnetic pole expansion angle θof an upper magnetic pole front end layer of the thin film head of thepresent invention;

[0040]FIG. 18 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the thickness Up1t of an uppermagnetic pole front end layer of the thin film head of the presentinvention;

[0041]FIG. 19 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the thickness of a high Bs layer ofan upper magnetic pole front end layer at the recording gap side of thethin film head of the present invention;

[0042]FIG. 20 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the distance Up2d from a floatingsurface to the front end of an upper magnetic pole top layer of the thinfilm head of the present invention;

[0043]FIG. 21 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the contact length Lc of an uppermagnetic pole front end layer and an upper magnetic pole top layer ofthe thin film head of the present invention;

[0044]FIG. 22 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the thickness Up2t of an uppermagnetic pole top layer of the thin film head of the present invention;

[0045]FIG. 23 is a diagram showing the distribution of medium in-planemagnetic field Hxz of the thin film head of the present invention;

[0046]FIG. 24 is a diagram showing another example of the distributionof medium in-plane magnetic field Hxz of the thin film head of thepresent invention;

[0047]FIG. 25 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the magnetic pole extension positionLy of an upper magnetic pole front end layer, i.e., the magnetic polecontraction position of the thin film head of the present invention bycomparing the presence of a projection step portion with the absencethereof;

[0048]FIG. 26 is a diagram showing the relation between the magneticpole expansion position Ly of an upper magnetic pole front end layer andthe medium in-plane magnetic field Hxzmax in the off-track position ofthe thin film head of the present invention;

[0049]FIG. 27 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the width Stw of a projection stepportion on a lower magnetic pole front end portion of the thin film headof the present invention;

[0050]FIG. 28 is a diagram showing the relation between the width Stw ofa projection step portion on a lower magnetic pole front end portion andthe medium in-plane magnetic field Hxzmax in the off-track position ofthe thin film head of the present invention;

[0051]FIG. 29 is a diagram showing the relation between the recordingmagnetic field intensity Hxmax and the starting position Std of aprojection step portion on a lower magnetic pole front end portion ofthe thin film head of the present invention; and

[0052]FIG. 30 is a diagram showing the relation between the startingposition Std of a projection step portion on a lower magnetic pole frontend portion and the medium in-plane magnetic field Hxzmax in theoff-track position of the thin film head of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0053] The present invention will be described hereinbelow in detail byembodiments.

[0054] <Embodiment 1>

[0055]FIG. 2 shows a cross-sectional view of a thin film head of thepresent invention. On a substrate 1 made of a non-magnetic material,there is provided a lower magnetic shield 2 made of a soft magneticmaterial for enhancing the reading resolution to eliminate the influenceof the external magnetic field. A reading gap 3 made of a non-magneticinsulating material is provided thereon. A reading element 4 consistingof an MR or GMR element is disposed in the reading gap. An uppermagnetic shield 21 is provided thereon. A separate layer 22 made of anon-magnetic material for separating a recording head and a reading headis provided thereon. A lower magnetic pole main layer 5, a lowermagnetic pole front end portion 23, and a lower magnetic pole rear endportion 24 are provided thereon. A non-magnetic insulating layer 25 isfilled between the lower magnetic pole front end portion 23 and thelower magnetic pole rear end portion 24.

[0056] The lower magnetic pole front end portion 23, the lower magneticpole rear end portion 24, and the non-magnetic insulating layer 25 areflattened by polishing. A recording gap layer 6, an upper magnetic polefront end layer 17, and an upper magnetic pole rear end layer 18 areprovided thereon. A second nonmagnetic insulating layer 19 and lowerlayer coils 8′ are provided. The surface of the upper magnetic polefront end layer 17, the upper magnetic pole rear end layer 18, and thesecond non-magnetic insulating layer 19 is flattened by polishing. Acoil insulating layer 7 and upper layer coils 8′ are disposed thereon.An upper magnetic pole top layer 20 is provided. The entire head isprotected by a protective layer 10. The front end of the upper magneticpole top layer is disposed so as to be recessed from a floating surface.

[0057] A rear end portion 26 of the upper magnetic pole top layer andthe upper magnetic pole rear end layer 18 are connected magnetically tothe lower magnetic pole rear end portion 24. The lower layer coils 8 andthe upper layer coils 8′ are constructed so as to be arrangedcircumferentially about the upper magnetic pole rear end layer 18 andthe rear end portion 26 of the upper magnetic pole top layer. Arecording electric current is applied to the lower layer coils 8 and theupper layer coils 8′. A magnetic flux is induced in the upper magneticpole front end layer 17, the upper magnetic pole top layer 20, the uppermagnetic pole rear end layer 18, the lower magnetic pole rear endportion 24, the lower magnetic pole main layer 5, and the lower magneticpole front end portion 23. A recording magnetic field generated from thefront end of the recording gap records a signal onto a recording medium14 moving slightly away from a floating surface 13.

[0058] In this embodiment, the upper magnetic shield 21 is separatedfrom the lower magnetic pole main layer 5 by the separate layer 22. Asin the prior art of FIGS. 3 and 4, the lower magnetic pole main layermay serve as the upper magnetic shield. The recording gap depth isdefined by the depth of the lower magnetic pole front end portion. Thesurface of the lower magnetic pole front end portion for defining therecording gap depth is formed so as to be almost perpendicular to therecording gap surface.

[0059]FIG. 1 shows a perspective view of the construction in thevicinity of the head front end of a thin film head of the presentinvention. This drawing shows only part of the lower magnetic pole mainlayer 5, the lower magnetic pole front end portion 23, the uppermagnetic pole front end layer 17, and the upper magnetic pole top layer20. As shown in the drawing, in the thin film head of the presentinvention, the lower magnetic pole front end portion 23 has a width Lp2wsmaller than the lower magnetic pole 5, a length (depth) correspondingto a gap depth Gd, and a height Lp2h. A portion opposite to the uppermagnetic pole by interposing the recording gap has a projection stepportion 27 having a width almost equal to a track width Tw of the uppermagnetic pole. The height of the projection step portion is called atrim depth Tr.

[0060] The upper magnetic front end layer 17 has a width almost equal tothe track width to a magnetic pole expansion position Ly in the headrear direction. The width is increased at an expansion angle θ from themagnetic pole expansion position Ly in the head rear direction to amaximum width Up1w. The length of the upper magnetic pole front endlayer 17 is Up1L, and the thickness is Up1t. The front end of the uppermagnetic pole top layer 20 is away from the floating surface by an uppermagnetic pole depth Up2d, and has a width Up2fw of the upper magneticpole front end and a thickness Up2t. The upper magnetic pole top layer20 has a shape to be increased at the expansion angle φ from acontraction position Up2Ly in the head rear portion to the uppermagnetic pole width Up2w. The upper magnetic pole top layer 20 is flatto a rising position Up2s of the upper magnetic pole top layer. Theupper magnetic pole top layer 20 from the Up2s is formed on the slope 15of the coil insulating layer.

[0061] In the thin film head of the present invention having theabove-mentioned construction, a magnetic field is calculated by computersimulation. The recording magnetic field intensity of the thin film headof the present invention is compared with that of the prior art thinfilm head shown in FIG. 4. The dimensions of the thin film head of thepresent invention are: track width Tw=0.35 μm, gap length Gl=0.13 μm,Gd=1 μm, Lp2w=8 μm, Tr=0.2 μm, Ly=0.8 μm, Up1t=2 μm, Up1L=3.5 μm, Up1w=4μm, θ=45°, Up2d=1 μm, Up2t=3 μm, Up2w=3 μm, Up2Ly=4 μm, Up2s=4 μm,φ=45°, and Up2w=26 μm. The change of the recording magnetic fieldintensity due to the change of the height Lp2h of the lower magneticpole front end portion 23 is calculated. The width Lp1w of the lowermagnetic pole 5 is 100 μm, and the thickness Lp1t of the lower magneticpole is 2 μm.

[0062] In the prior art thin film head shown in FIG. 4, the thicknessIlh of the first non-magnetic insulating layer 16 for determining thegap depth is 0.4 μm, the film thickness Lp1t of the lower magnetic polemain layer 5 is 2.5 μm, and other dimensions are the same as those ofthe thin film head of the present invention.

[0063] As a magnetic material for use in the thin film head of thepresent invention, a 46Ni—Fe film (a saturation magnetic flux densityBs=1.68T) is used for the lower magnetic pole main layer 5 and the uppermagnetic pole top layer 20. A CoNiFe film (Bs=2.0T) is used for thelower magnetic pole front end portion 23, the lower magnetic pole rearend portion 24, the upper magnetic pole front end layer 17, and theupper magnetic pole rear end layer 18. The same material as that of thethin film head of the present invention is used for the prior art thinfilm head. The lower magnetic pole 5 is a CoNiFe film (Bs=2.0T) forcomparison.

[0064]FIG. 11 shows maximum magnetic field intensity Hxmax in the mediumrunning direction in the position as the medium center away by 25 nmfrom the floating surface, in the center position of the track width.This value is called a magnetic field intensity. As shown in thedrawing, the magnetic field intensity of the prior art thin film head isabout 9000 Oe. The magnetic field intensity of the thin film head of thepresent invention in the case of a height Lp2h=0.3 μm of the lowermagnetic pole front end portion is higher than that of the prior artthin film head. With increase of the Lp2h, the magnetic field intensityof the thin film head of the present invention is increased abruptly.Increase of the magnetic field intensity is saturated at the Lp2h of 1μm or more. The reason why the magnetic field intensity is increasedwith the Lp2h lies in that since the distance between the upper magneticpole front end layer 17 and the upper magnetic pole top layer 20, andthe lower magnetic pole 5 is increased, it is thus considered that theleakage flux therebetween is reduced, so that the magnetic flux reachesin the vicinity of the recording gap of the front end of the head withless decay.

[0065] As described above, the lower magnetic pole front end portion 23is provided, and the height Lp2h is 1 μm or more. As compared with theprior art thin film head, the magnetic field intensity can be largelyincreased by about 600 Oe or more. The increase of the magnetic field isvery advantageous for recording a signal having a high density onto ahigh-coercivity medium.

[0066] When the lower magnetic pole front end portion 23 is provided, aphotoresist for producing the upper magnetic pole front end layer can beformed on the flat surface. Unlike the prior art, deterioration of thetrack width accuracy due to abnormal reflection due to the step forexposure or insufficient depth of focus can be eliminated. A small trackwidth can be formed at high accuracy.

[0067] The height Lp2h of the lower magnetic pole front end portion is0.3 μm or more as shown in FIG. 11 to provide the effect of increasingthe magnetic field intensity as compared with the prior art, and is 0.7μm or more to provide the sufficient effect of increasing the magneticfield. As the magnetic head, the change of the magnetic field ispreferably small when the respective parts of the head are changed. Inview of this, the Lp2h is more preferably 0.7 μm or more forsufficiently increasing the magnetic field and decreasing the change ofthe magnetic field.

[0068] When the Lp2h is too large, the gap between the recording gap andthe reading gap is increased to impose the following problem. The gapbetween the recording gap and the reading gap is too large, so as toincrease a deviation of the position of the reading track and therecording track on the magnetic disk. It is thus difficult to controlthe track position. As the gap between the recording gap and the readinggap is increased, a region for recording a signal onto the magnetic diskis small so as to lower the format efficiency. From such a problem, therecording and reading gap must be less than 6 μm.

[0069] In the thin film head of the present invention, the gap betweenthe center of the reading element 4 and the upper shield 21 is 0.04 μm,the thickness of the upper shield 21 is 1.3 μm, the thickness of theseparate layer 2 is 0.5 μm, the thickness of the lower magnetic polemain layer 5 is 2 μm, and the distance between the upper end of thelower magnetic pole front end portion and the center of the recordinggap is 0.065 μm. In order that the recording and reading gap is lessthan 6 μm, an allowance of about 0.1 μm is provided and the height Lp2hof the lower magnetic pole front end portion must be 2 μm or less. Toprovide an allowance to the variation of the dimensions, the Lp2h ismore preferably 1.5 μm or less.

[0070]FIG. 12 shows the change of the magnetic field intensity when thewidth Lp2w of the lower magnetic pole front end portion is changed. Theheight Lp2h of the lower magnetic pole front end portion is 1.4 μm.Other shapes are the same as those of FIG. 11. As shown in the drawing,with increase of the Lp2w, the magnetic field intensity is increasedabruptly, and is maximum at the Lp2w of about 3 μm, thereafter it isdecreased gradually.

[0071] The magnetic field intensity is low when the Lp2w is below 3 μm,because it is considered that the lower magnetic pole front end portionis considered to cause magnetic saturation. The magnetic field isdecreased gradually when the Lp2w is above 3 μm, because it isconsidered that, when the Lp2w is large, the leakage flux from the uppermagnetic pole to the end portion of the lower magnetic pole front endportion is increased to relatively decrease the magnetic flux in thevicinity of the recording gap.

[0072] The Lp2w is desirably 1 μm or more. When the Lp2w is 1 μm ormore, a magnetic field intensity sufficiently higher than that of theprior art thin film head can be obtained. When the Lp2w is less than 3μm, the change of the magnetic field due to variation of the Lp2w islarge. In order that a stable magnetic field intensity can be obtainedto the change of the Lp2w, the Lp2w is more preferably 3 μm or more.When the Lp2w is 3 μm or more, the magnetic field intensity is decreasedgradually.

[0073] In the thin film head of the present invention, to obtain a highmagnetic field intensity, as the material of the lower magnetic polefront end portion, a magnetic material having a high saturation magneticflux density Bs of above 1.6T, preferably 1.8 to 2.2T. Specificmaterials include an Ni—Fe film or Co—Fe—Ni film having 46 Ni as a maincomposition. These high Bs films, particularly, the Co—Fe—Ni film itselfhaving a high saturation magnetic flux density Bs of 1.8 to 2.2Tgenerally has a problem of corrosion resistance. When the protectivefilm is deposited on the floating surface, any problem such as corrosioncannot be caused. The floating surface protective film is formed verythinly so as to have a thickness of 3 to 6 nm. When a fine polishingscratch during polishing the floating surface remains, the floatingsurface protective film cannot sufficiently cover the scratch and thescratch may remain as defect. In this case, in the cleaning process ofthe producing processing after that, corrosion can be caused from thisdefect portion. To prevent this and enhance the producing yield, theexposing width of the lower magnetic pole front end portion using thehigh Bs film to the floating surface must be reduced.

[0074] With increase of the recording density in recent years, theflying height of the floating surface on the recording medium surfacemust be reduced. For this reason, the width of the floating surface ofthe slider equipped with the thin film head in the track width directionmust be reduced. The upper magnetic shield 2, the lower magnetic shield21, the lower magnetic pole main layer 5, or the lower magnetic polefront end portion 23 of the head outside the floating surface width ofthe slider is subject to groove processing by ion milling during grooveprocessing of the slider and a step is formed to the floating surface,when the floating surface width of the slider in the position of thethin film head is smaller than the width of the upper magnetic shield 2,the lower magnetic shield 21, the lower magnetic pole main layer 5, orthe lower magnetic pole front end portion 23 of the head.

[0075] The floating surface protective film is formed by the processingafter that. As described above, the protective film is formed to be verythin. When the projection step portion cannot be protected sufficiently,the protective film can be defected. When the lower magnetic pole frontend portion having a high Bs and low corrosion resistance has a widthlarger than the floating surface width, corrosion can be caused in theprojection step portion. The floating surface width of the slider in theposition of the thin film head tends to be reduced from about 200 μm ofthe prior art to about 60 μm or less. Based on these, to reduce thedefect percentage due to corrosion of the lower magnetic pole front endportion and to enhance the producing yield, a margin of the processingdimension shift is provided so that the width Lp2w of the lower magneticpole front end portion must be 50 μm or less, and more preferably, 30 μmor less.

[0076]FIG. 13 shows the change of magnetic field intensity when the gapdepth Gd is changed. The height Lp2h of the lower magnetic pole frontend portion is 1.4 μm. Other shapes are the same as those of FIG. 11.Since the Gd is 2 μm, the magnetic field intensity is increased withdecrease of the Gd. When the Gd is about 0.3 μm, the magnetic fieldintensity is maximum. When the Gd is less than 0.3 μm, the magneticfield intensity is decreased abruptly. With the Gd of less than 0.3 μm,the magnetic field intensity is decreased, because the lower magneticpole front end portion is magnetic-saturated. With the Gd of 0.3 μm ormore, the magnetic field intensity is decreased, because with increaseof the Gd, the magnetic flux passing through the gap depth side of thelower magnetic pole front end portion is increased, so that theconcentration of the magnetic flux in the vicinity of the recording gapof the floating surface side is reduced.

[0077] When the Gd is less than 0.3 μm, a high magnetic field can beobtained. However, the change of the magnetic field due to the change ofthe Gd is steep, so that the recording characteristics are likely to bevaried. When the Gd is less than 0.3 μm, the mechanical strength of thelower magnetic pole front end portion is reduced, and a problem such aspeeling is likely to be caused. The Gd is thus desirably 0.3 μm or more.When the Gd exceeds 2 μm, the magnetic field intensity is reducedlargely. The Gd is preferably 2 μm or less.

[0078]FIG. 14 shows the change of the magnetic field intensity of thetrim depth Tr. The height Lp2h of the lower magnetic pole front endportion is 1.4 μm. Other shapes are the same as those of FIG. 11. Asshown in the drawing, the magnetic field intensity is decreased as thetrim depth Tr is increased. To obtain the magnetic field intensity abovethat of the prior art head, the Tr is desirably 0.4 μm or less. When theTr is less than 0.1 μm, the magnetic field intensity is almost constant.When the Tr is less than 0.1 μm, the medium in-plane magnetic fieldcomponent in the position away from the center of the track to theoutside of the track end portion is not reduced sufficiently. Themagnetic field intensity becomes a value close to the medium coercivityor exceeding the medium coercivity. In such a case, an erasing width Twefor erasing a signal by the recording head is unnecessarily larger thana recording signal width Tww. In some cases, the signal of the adjacenttrack will be erased or decayed. The trim depth must be 0.1 μm or more.

[0079] In the thin film head of the present invention, as in the shapeof the lower magnetic pole front end portion shown in FIG. 5(a), a taperangle α can be provided to an upper end surface 28 of the lower magneticpole front end portion. FIG. 15 shows the change of the magnetic fieldintensity with the taper angle α. The height Lp2h of the lower magneticpole front end portion is 1.4 μm. Other shapes are the same as those ofFIG. 11. When the taper angle is provided to the upper end surface ofthe lower magnetic pole front end portion, the leakage flux from theupper magnetic pole front end layer to the end portion of the lowermagnetic pole front end portion is decreased so as to increase themagnetic field intensity.

[0080] As shown in FIG. 15, with increase of the taper angle α, themagnetic field intensity is increased. The magnetic field intensity ismaximum at α=20° to 40°, and then is decreased. The magnetic fieldintensity is decreased at the taper angle of above 40° because the lowermagnetic pole front end portion is saturated. The taper angle α ispreferably 60° or less for obtaining the effect for increasing themagnetic field. FIG. 5(b) shows an example in which the lower magneticpole front end portion has two or more upper end surfaces 28 and 28′ andtwo or more taper angles α and α′. When the taper angle has two or morevalues, the effect of increasing the magnetic field by the taper anglesis provided likewise.

[0081]FIG. 16 shows the change of the magnetic field intensity with themagnetic pole expansion position Ly of the upper magnetic pole front endlayer described in the description of FIG. 1. The height Lp2h of thelower magnetic pole front end portion is 1.4 μm. Other shapes are thesame as those of FIG. 11. With decrease of the Ly, the magnetic fieldintensity is increased largely. When the Ly exceeds 1.5 μm, the magneticfield intensity is lower than the magnetic field intensity 9000 Oe ofthe prior art head. The Ly is preferably 1.5 μm or less. As the Ly isdecreased, the magnetic field intensity is increased. However, from thelimit of the resolution of the photoresist, a radius of curvature R ofat least about 0.2 μm is provided in the vicinity of the Ly. When the Lyis less than 0.2 μm, the change of the track width by the processingaccuracy of the Ly. To ensure a Tw width accuracy, the Ly is preferably0.2 μm or more.

[0082] In the prior art thin film head shown in FIG. 3 or 4, the uppermagnetic pole 9 or the upper magnetic pole front end layer 17 fordefining the track width is formed on the slope 15 of the coilinsulating layer or the projection step of the first insulating layer16. When the magnetic pole expansion position Ly is set in the vicinityof the gap depth Gd, the track width in the vicinity of the Ly isaffected by the magnetic pole expansion shape by the reflection ofexposure from the slope or the projection step so as to increase anerror. The Ly must be at least 0.3 μm or more larger than the Gd. In theprior art thin film head, it is difficult to largely reduce the Ly toincrease the magnetic field intensity.

[0083] In the thin film head of the present invention, as describedabove, the upper magnetic pole front end layer for defining the trackwidth can be formed on the flat surface of the lower magnetic pole frontend portion. The positional relation between the Ly and Gd as describedabove is not limited. As shown in FIGS. 7 and 11, in the thin film headof the present invention, the change of the magnetic field intensitywith the Ly is larger than the change of magnetic field intensity withthe Gd. The Ly is smaller than the Gd so as to realize a thin film headhaving a high magnetic field intensity.

[0084] The curve (a) of the FIG. 17 shows the change of the magneticfield intensity with the expansion angle θ of the upper magnetic polefront end layer. The height Lp2h of the lower magnetic pole front endportion is 1.4 μm. Other shapes are the same as those of FIG. 11. Asshown in the drawing, with increase of θ, the magnetic field intensityis increased, which is then increased gently at 45° or more. When theexpansion angle θ of the upper magnetic pole front end layer is toolarge, the radius of curvature R in the vicinity of the Ly is increasedby scattering of light in the resist when exposing the resist, so thatthe track width accuracy tends to be reduced. To prevent this, theexpansion angle θ is preferably 60° or less, more preferably, below 50°or less. When the expansion angle θ is less than 20°, the magnetic fieldintensity is reduced significantly. The expansion angle θ is preferably20° or more, more preferably, 30° or more.

[0085] As in the plane shape of the upper magnetic pole front end layershown in FIG. 6, using the two or more expansion angles and Ly of theupper magnetic pole front end layer, there is provided a two-stage shapein which an expansion angle θ2 in an expansion position Ly2 of the headrear portion side is larger than an expansion angle θ1 of an expansionposition Ly1 of the head front end side. The reduction of the magneticfield intensity can be released. The processing accuracy in the vicinityof the Ly1 for determining the track width can be enhanced. As such anexample, the curve (b) of FIG. 17 shows the change of the magnetic fieldintensity with θ1 when Ly1=0.8 μm, Ly2=1.3 μm, and θ2 is 45°. Thetwo-stage shape can increase the magnetic field intensity in the smallregion at θ1. As a result, the minimum value capable of using theexpansion angle θ1 of the head front end side can be reduced to 10°.

[0086]FIG. 18 shows the change of the magnetic field intensity with thefilm thickness Up1t of the upper magnetic pole front end layer. Theheight Lp2h of the lower magnetic pole front end portion is 1.4 μm. Thecurve (a) of FIG. 18 shows the case that the depth Up2d of the uppermagnetic pole is 1 μm, and the curve (b) thereof shows the case that theUp2d is 0.5 μm. Other shapes are the same as those of FIG. 11. As shownin the curve (a), when the Up2d is 1 μm, with increase of the filmthickness Up1t of the upper magnetic pole front end layer, the magneticfield intensity is increased abruptly and is maximum at the filmthickness of 2 to 3 μm. Thereafter the magnetic field intensity isdecreased gradually. When the Up2d is 0.5 μm, decrease of the magneticfield intensity is less in the region having the small Up1t. Themagnetic field is reduced in the region having the small film thickness;it is considered that the magnetic path width is reduced when themagnetic flux from the upper magnetic pole top layer is transmitted inthe vicinity of the recording gap of the front end of the head. Themagnetic field is reduced in the region having the large film thickness;it is considered that when the film thickness is too large, the distancebetween the upper magnetic pole top layer and the portion in thevicinity of the recording gap of the front end of the head is long so asto increase the magnetic path length. When the Up2d is small, thedistance between the upper magnetic pole top layer and the recording gapof the front end of the head is short so as to increase the magneticfield intensity.

[0087] As shown in the drawing, to obtain a high magnetic fieldintensity, the film thickness Up1t of the upper magnetic pole front endlayer is 0.5 μm or more, desirably, 1 μm or more. When the Up2d issmall, a high magnetic field can be obtained when the Up1t is less than0.5 μm. When the Up1t is less than 0.5 μm, the change of the magneticfield intensity by film thickness variation is large. The Up1t isdesirably 0.5 μm or more. When the Up1t exceeds 4 μm, the magnetic fieldintensity starts to be reduced. The Up1t is desirably 4 μm or less.

[0088] The film thickness of the upper magnetic pole front end layeraffects not only the magnetic field intensity but also the track widthaccuracy. When the upper magnetic pole front end layer is thick, theresist for forming the upper magnetic pole front end layer must be alsothick. When the resist is thick, the scattering of light in the resistis increased to reduce the resolution. The track width accuracy is alsolowered. The magnetic field intensity is ensured, and in order toenhance the track width accuracy, the film thickness Up1t of the uppermagnetic pole front end layer is more preferably 3 μm or less.

[0089] In the above-mentioned example, there is described the magneticfield intensity when the entire upper magnetic pole front end layer isconstructed by CoNiFe of 2.0T. As described above, in the thin film headof the present invention, basically, the upper magnetic pole front endlayer 17, the upper magnetic pole rear end layer 18, and the secondnon-magnetic insulating layer 19 are formed. Then, these surfaces areflattened by polishing. The upper layer coils 8′, the coil insulatinglayer 7, and the upper magnetic pole top layer 20 are formed. When theupper magnetic pole front end layer 17 is polished and a CoNiFe platedfilm having a high saturation magnetic flux density is used as the uppermagnetic pole front end layer, the corrosion resistance of this film islow, so that corrosion may occur to the polishing liquid. To preventcorrosion of CoNiFe for such polishing, the upper magnetic pole frontend layer is of a two-layer construction so that a 46Ni—Fe film islaminated on the CoNiFe film. The CoNiFe film cannot be exposed duringpolishing.

[0090]FIG. 19 shows the change of magnetic field intensity with the filmthickness Up1hbt of the high Bs film of the recording gap side in thecase of using a multi-layered film in which a side adjacent to therecording gap layer of the upper magnetic pole front end layer is amagnetic film of 2.0T, and a side adjacent to the upper magnetic poletop layer is a magnetic film of 1.68T. The film thickness Up1t of theentire upper magnetic pole front end layer is 2 μm, and the height Lp2hof the lower magnetic pole front end portion is 1.4 μm. Other shapes arethe same as those of FIG. 11. As shown in the drawing, with increase ofthe Up1hbt, the magnetic field intensity is increased abruptly, which isthen increased gently at the Up1hbt of 0.5 μm or more. When the uppermagnetic pole front end layer is a multi-layered film of a high Bs filmand a lower Bs film, the film thickness of the high Bs film of therecording gap side is 0.2 μm or more to obtain a high magnetic field.When the Up1hbt is less than 0.5 μm, the magnetic field intensity isreduced significantly with the film thickness, and it is preferably 0.5μm or more.

[0091]FIG. 20 shows the change of the magnetic field intensity with thedistance between the floating surface and the front end of the uppermagnetic pole top layer, that is, with the depth Up2d of the uppermagnetic pole top layer. The height Lp2h of the lower magnetic polefront end portion is 1.4 μm. Other shapes are the same as those of FIG.11. With increase of the Up2d, the magnetic field intensity is decreasedgradually, and is reduced largely at the Up2d of 1.5 μm or more. Asdescribed above, the Up2d may be decreased to enhance the magnetic fieldintensity. When the Up2d is too small, the leakage field from the endportion of the upper magnetic pole top layer can erase or decay arecording signal of the medium. When the Up2d is 0.2 μm, the leakagefield generated from the end portion of the upper magnetic pole toplayer is below 1500 Oe in the medium center position (25 nm from thefloating surface). When Up2d=0, that is, the front end of the uppermagnetic pole top layer is exposed from the floating surface, theleakage field reaches 3000 Oe. Some media used can erase or decay asignal recorded onto the medium. The Up2d is 0.2 μm or more to avoid theforegoing problem. When the Up2d is increased, the magnetic fieldintensity is decreased, so that the Up2d is 2 μm or less, preferably,1.5 μm or less.

[0092] In FIG. 20, with increase of the Up2d, the magnetic fieldintensity is decreased, because the contact length Lc of the uppermagnetic pole top layer and the upper magnetic pole front end layer isshort. The contact length Lc corresponds to a difference between thelength Up1L of the upper magnetic pole and the depth Up2d of the uppermagnetic pole top layer shown in FIG. 1.

[0093]FIG. 21 shows the change of the magnetic field intensity with thecontact length Lc of the upper magnetic pole front end layer and theupper magnetic pole top layer. As shown in the drawing, with the contactlength Lc, the magnetic field intensity is increased abruptly, and isincreased gently at the Lc of 2 μm or more. To obtain a high magneticfield intensity, the Lc must be 1.5 μm or more. When the Lc is less than2 μm, the change of the magnetic field with the Lc is large. The Lc ispreferably 2 μm or more.

[0094] The length Up1L of the upper magnetic pole front end layer andthe rising position Up2s of the upper magnetic pole top layer areincreased so that the contact length Lc can be long. In such a case, thedistance between the gap depth and a back contact position Bc forcontacting the upper magnetic pole rear end layer, the lower magneticpole rear end portion and the lower magnetic pole is long, therebyincreasing the magnetic path length of the entire head. The changingrate of the magnetic field is low so as to deteriorate the recordingcharacteristics at a high frequency.

[0095] The Up1L is 5 μm or less, preferably, 4 μm or less so as toensure the contact length Lc. A difference between the rising positionUp2s of the upper magnetic pole top layer and the Up1L (Up2s Up1L) isdesirably 0 to 1.5 μm, so that when the alignment of the upper magneticpole top layer and the upper magnetic pole front end layer is shifted,the contact length Lc can be ensured.

[0096]FIG. 22 shows the change of the magnetic field intensity with thefilm thickness Up2t of the upper magnetic pole top layer. The heightLp2h of the lower magnetic pole front end portion is 1.4 μm. Othershapes are the same as those of FIG. 11. As shown in the drawing, withthe film thickness Up2t of the upper magnetic pole top layer, themagnetic field intensity is increased abruptly, and the increase issaturated at the Up2t of 2 μm or more. To obtain a high magnetic fieldintensity, the Up2t must be 1.5 μm or more. On the other hand, to obtaina stable magnetic field intensity to the variation of the Up2t, the Up2tis desirably 2 μm or more. When the Up2t is too large, the magneticfield intensity at a high frequency tends to be reduced by theovercurrent effect. The Up2t is desirably 4 μm or less.

[0097] As described above, in the thin film head of the presentinvention, the lower magnetic pole front end portion is provided toselect its shape. A recording magnetic field higher than that of theprior art thin film head can be obtained. The photoresist for producingthe upper magnetic pole front end layer can be formed on the flatsurface of the lower magnetic pole front end portion. The processingaccuracy of the small track width can be enhanced.

[0098] <Embodiment 2>

[0099] As described in Embodiment 1, the thin film head of the presentinvention can realize a high recording magnetic field. When therecording magnetic field is very high in the thin film head of thepresent invention, the medium in-plane magnetic field is found to beincreased in the position away from the center of the track to theoutside of the track end portion in the track width direction (theoff-track position). The medium in-plane magnetic field refers to avector sum Hxz of the magnetic field component in the recording mediumrunning direction and the magnetic field component in the track widthdirection. When the medium in-plane magnetic field in the off-trackposition is large, the signal of the adjacent track recorded onto themedium can be erased or decayed. The medium in-plane magnetic field inthe off-track position is desirably as small as possible. The secondembodiment of the present invention proposes a construction for reducingthe medium in-plane magnetic field in the off-track position.

[0100]FIG. 7 shows a perspective view of the front end portion of thethin film head of the second embodiment of the present invention. In thethin film head of Embodiment 1, it is considered that the leakage fluxfrom the upper magnetic pole front end layer is concentrated in thevicinity of the end portion of the floating surface of the lowermagnetic pole front end portion, thereby increasing the medium in-planemagnetic field in the off-track position. To reduce this, in the secondembodiment, a projection step portion 29 for absorbing the leakage fluxis provided on the lower magnetic pole front end portion 23. In thedrawing, the width of the projection step portion 29 from the uppermagnetic pole front end layer is Stw, and the starting position of theprojection step portion 29 from the floating surface is Std.

[0101]FIG. 23 shows the comparison of the medium in-plane magnetic fieldHxz in the case that the Stw of the projection step portion 29 is zeroin the lower magnetic pole front end portion (which corresponds to theabsence of a portion larger than the width of the upper magnetic pole inthe projection step portion 29). FIG. 24 shows the comparison of themedium in-plane magnetic field Hxz in the case that the Stw of theprojection step portion 29 is not zero in the lower magnetic pole frontend portion (which corresponds to the presence of a portion larger thanthe width of the upper magnetic pole in the projection step portion 29.In this example, Stw=3.8 μm).

[0102] In these examples, Ly=0.5 μm, Std=0.5 μm, Lp2h=1.4 μm, and otherconditions are the same as those of FIG. 11. The drawing shows themagnetic field distribution in the medium in-plane direction Hxz in theposition corresponding to the center of the medium when the head isviewed from the floating surface (25 nm from the floating surface), inwhich the right half from the track center z=0 of the head is shown. Thehorizontal axis z shows a position from the track center. Z=0 to 0.175μm indicates a track width, and above z=0.175 μm indicates an off-trackposition. The vertical axis x shows a position in the medium runningdirection. Below x=−0.13 μm indicates the lower magnetic pole front endportion, x=−0.13 to 0 μm indicates the recording gap, and above x=0indicates the upper magnetic pole front end layer.

[0103] As shown in FIG. 23, when the Stw of the projection step portion29 is 0, the in-plane magnetic field component Hxz of z=0.45 μm largelyaway from the end portion of the track (z=0.175) exceeds 4000 Oe. Somemedia used can erase or decay a signal recording onto the adjacenttrack.

[0104] When the Stw of the projection step portion 29 is not 0 (in thiscase, Stw=3.8 μm), as shown in FIG. 24, the in-plane magnetic fieldcomponent of z=0.45 μm is lowered to below about 4000 Oe to reduce theinfluence onto the adjacent track.

[0105] In the case that the Stw of the projection step portion 29 is not0 or is 0, FIG. 25 shows the change of the magnetic field intensityHxmax at the center of the track width when the magnetic pole expansionposition of the upper magnetic pole front end layer, that is, the uppermagnetic pole contraction position Ly is changed; and FIG. 26 shows thechange of the maximum value Hxzmax at z=0.45 μm of the medium in-planemagnetic field with the magnetic pole expansion position Ly of the uppermagnetic pole front end layer. The curve (a) shows the case that the Stwof the projection step portion 29 is 0, and the curve (b) shows the casethat the Stw of the projection step portion 29 is not 0. Std=Ly, andother conditions are the same as those of FIG. 23. As shown in FIG. 25,as compared with the magnetic field intensity of the center of the trackwidth, the magnetic field intensity is reduced by below 100 Oe when theStw of the projection step portion 29 is not 0. The influence onto thecenter magnetic field due to the projection step portion 29 provision issmall. As shown in FIG. 26, the medium in-plane magnetic field Hxmax atz=0.45 μm can be reduced largely by the projection step portion 29provision as described above. In particular, the effect is significantin a small region of Ly having a high center magnetic field.

[0106]FIG. 27 shows the change of the center magnetic field intensityHxmax with the width Stw of the projection step portion 29. FIG. 28shows the change of the maximum value Hxmax of the medium in-planemagnetic field at z=0.45 μm with the width Stw of the projection stepportion 29. Ly=Std=0.5 μm, and other conditions are the same as those ofFIG. 25. In the drawings, Stw=0 corresponds to the absence of a portionlarger than the width of the upper magnetic pole in the projection stepportion 29. As shown in FIG. 27, the Stw hardly changes the centermagnetic field. As shown in FIG. 28, the medium in-plane magnetic fieldat z=0.45 μm is increased when the Stw is less than 0.5 μm, so that theeffect of the projection step portion 29 provision is reduced. The widthStw of the projection step portion 29 must be 0.5 μm or more.

[0107]FIG. 29 shows the change of the center magnetic field Hxmax withthe distance Std between the starting position of the projection stepportion 29 on the lower magnetic pole front end portion and the floatingsurface. FIG. 30 shows the change of the maximum value Hxzmax of themedium in-plane magnetic field at z=0.45 μm with the distance Stdbetween the starting position of the projection step portion 29 on thelower magnetic pole front end portion and the floating surface. The Stwis 3.8 μm, and other conditions are the same as those of FIGS. 27 and28. Since Gd=1, Std=1 corresponds to the case of the absence of theprojection step portion 29. As shown in FIG. 29, the center magneticfield is increased slightly with decrease of the Std. On the other hand,the medium in-plane magnetic field at z=0.45 μm is decreased withdecrease of the Std. Therefore, as a portion larger than the width ofthe upper magnetic pole is provided in the projection step portion 29,at any Std, the medium in-plane magnetic field in the off-track positionis reduced. The effect that the starting position Std of the projectionstep portion is below the Ly is high and more preferable. When the Stdis too small, the effect of trimming is reduced so as to increase themedium in-plane magnetic field in the off-track position. The Std isdesirably 0.1 μm or more.

[0108] There are some methods for forming the projection step portion 29in this embodiment. For example, after the lower magnetic pole front endportion 23, the recording gap layer 6, and the upper magnetic pole frontend layer 17 are formed, the unnecessary portion of the lower magneticpole front end portion is removed by FIB (focused ion beam), wherebytrack trimming and corresponding to the projection step portion 27 shownin FIG. 1 and the projection step portion 29 can be formed at the sametime. In addition, after the upper magnetic pole front end layer 17 isformed, a protective resist is formed in a portion to be the projectionstep portion 29 on the lower magnetic pole front end portion on thelower magnetic pole front end portion, so that using the protectiveresist as a mask, the unnecessary portion is removed by ion milling,thereby forming track trimming and the projection step portion 29.

[0109] In the thin film head of the present invention, the projectionstep portion 29 on the lower magnetic pole front end portion is formedby removing the lower magnetic pole front end portion except for thetrack width as in the prior art trimming. The projection step portion 29appears to be similar to the prior art track trimming. The prior arttrack trimming is processed by ion milling using the upper magnetic polefront end layer as a mask so as to be formed in almost the same shape ofthat of the upper magnetic pole front end layer. The projection stepportion 29 of the present invention, as shown in FIG. 7, has a widthlarger than the upper magnetic pole front end layer at least in the headrear portion from the floating surface, so as to absorb the leakage fluxfrom the upper magnetic pole front end layer in a portion larger thanthe upper magnetic pole front end layer.

[0110] As shown in FIG. 8, various shapes are possible as the shape ofthe projection step portion larger than the upper magnetic pole frontend layer, so as to provide the effect of reducing the medium in-planemagnetic field in the off-track position. The height of the projectionstep portion 29 is almost equal to the trim depth Tr. However, it ispossible to provide the effect when the height of the projection stepportion 29 is smaller than the trim depth Tr.

[0111] <Embodiment 3>

[0112] In Embodiments 1 and 2, the example in which the track width is0.35 μm is described. When the track width has a value other than theabove-mentioned value, the dimensions of the respective parts of thehead are changed in proportion to the track width. The change of themagnetic field intensity is found to be the same as in Embodiments 1 and2. The selection range of the dimensions of the respective parts whenthe track width Tr is changed is as follows.

[0113] (a) The ratio Lp2h/Tw of the height Lp2h of the lower magneticpole front end portion to the track width Tw is 0.9 or more, morepreferably, 2 or more.

[0114] (b) The ratio Lp2w/Tw of the width Lp2w of the lower magneticpole front end portion to the track width Tw is 2.9 or more, morepreferably, 8.6 or more.

[0115] (c) The ratio Gd/Tw of the gap depth Gd to the track width Tw is0.9 to 5.7.

[0116] (d) The ratio Tr/Tw of the trim depth Tr to the track width Tw is0.29 to 1.15.

[0117] (e) The ratio Ly/Tw of the magnetic pole expansion position Ly tothe track width Tw is 0.6 to 4.3.

[0118] (f) The ratio Up1t/Tw of the film thickness Up1t of the uppermagnetic pole front end layer to the track width Tw is 1.4 to 11.4, morepreferably 2.9 to 8.6.

[0119] (g) The ratio Up1hbt/Tw of the high Bs film thickness Up1hbt ofthe upper magnetic pole front end layer to the track width Tw is 0.6 ormore, more preferably, 1.4 or more.

[0120] (h) The ratio Up2d/Tw of the depth Up2d of the upper magneticpole top layer to the track width Tw is 0.6 to 5.7, more preferably, 0.6to 4.3.

[0121] (i) The ratio Lc/Tw of the contact length Ic of the uppermagnetic pole top layer and the upper magnetic pole front end layer tothe track width Tw is 4.3 or more, more preferably, 5.7 or more.

[0122] (j) The ratio Up1L/Tw of the length Up1L of the upper magneticpole top layer to the track width Tw is 14.3 or less, more preferably,11.4 or less.

[0123] (k) The ratio Up2t/Tw of the film thickness Up2t of the uppermagnetic pole top layer to the track width Tw is 4.3 to 11.4, morepreferably, 5.7 to 11.4.

[0124] (l) The ratio Stw/Tw of the width Stw of the projection stepportion on the upper magnetic pole front end layer to the track width Twis 1.4 or more.

[0125] (m) The ratio of the starting position Std of the projection stepportion on the upper magnetic pole front end layer to the track width Twis 0.3 or more.

[0126] By using the shapes described above, as in Embodiments 1 and 2,it is possible to obtain a thin film head having a high track widthaccuracy, a high recording magnetic field intensity, and a small mediumin-plane magnetic field in the off-track position.

[0127] In the thin film head of the present invention shown inEmbodiments 1, 2 and 3, as shown in FIG. 2, the example in which theupper magnetic pole front end layer is provided. As shown in FIG. 9, thehead not using the upper magnetic pole front end layer is combined withthe lower magnetic pole front end portion 23 to provide the same effect.In this case, the upper magnetic pole front end layer 17 corresponds tothe upper magnetic pole front end portion of FIG. 9.

[0128] In addition, in the thin film head of the present invention shownin Embodiments 1, 2 and 3, as shown in FIG. 2, the lower layer coils 8are disposed between the upper magnetic pole front end layer 17 and theupper magnetic pole rear end layer 18 so as to be arrangedcircumferentially about the upper magnetic pole rear end layer 18.However, as shown in FIG. 10(a), both the lower layer coils 8 and theupper layer coils 8′ may be disposed in the coil insulating layer 7 soas to be arranged circumferentially about the rear end portion 26 of theupper magnetic pole top layer.

[0129] As shown in FIG. 10(b), the lower layer coils 8 may be disposedbetween the lower magnetic pole front end portion 23 and the lowermagnetic pole rear end portion 24 so as to be arranged circumferentiallyabout the lower magnetic pole rear end portion 24, and the upper layercoils 8′ may be disposed between the upper magnetic pole front end layer17 and the upper magnetic pole rear end layer 18 so as to be arrangedcircumferentially about the upper magnetic pole rear end layer 18. Theconstruction of FIG. 2 may house only the upper layer coils 8′ in thecoil insulating layer 10. The construction of FIG. 2 can reduce theheight of the upper magnetic pole rear end layer 18 so as to decreasethe magnetic path length of the entire head. As compared with theconstruction of FIG. 10(a), the construction of FIG. 2 can increase themagnetic field rising rate at a high frequency so as to enhance therecording characteristics at a high frequency.

[0130] In the construction of FIG. 10(b), the coil insulating layer 7 isunnecessary so as to reduce the magnetic path length of the entire head.In the above-mentioned embodiments, the coils are arranged in two layersof an upper layer and a lower layer. The coils may be arranged in onelayer or three or more layers to provide the same effect.

[0131] In the above-mentioned embodiments, the CoNiFe film is describedas the magnetic material for use in the lower magnetic pole front endportion and the upper magnetic pole front end layer of the thin filmhead of the present invention. The magnetic material is not limitedthereto when it is a soft magnetic material having a high saturationmagnetic flux density. For example, the magnetic material can include a46Ni—Fe film with Bs=1.6 to 1.7T, a CoNiFe film or a Co—Fe film withBs=1.8 to 2.4T, and so on.

[0132] It is possible to use not only a plated film but also a sputterfilm such as CoNiFe film, Co—Fe film, Co—Fe—N film, and Fe—Ta—N film.The magnetic field intensity of the thin film head of the presentinvention is affected greatly by the saturation magnetic flux density ofthe magnetic material for use in the upper magnetic pole front end layerand the lower magnetic pole front end portion. The saturation magneticflux density of the magnetic material for use in the upper magnetic polefront end layer and the lower magnetic pole front end portion must be atleast 1.6T or more. More preferably, it is 1.8T or more.

[0133] The 46Ni—Fe film is described as the magnetic material for use inthe lower magnetic pole and the upper magnetic pole top layer of thethin film head of the present invention. The magnetic material is notlimited thereto when it is a soft magnetic material having a highsaturation magnetic flux density. In addition to a plated film such as a46Ni—Fe film with Bs=1.6 to 1.7T and an 82Ni—Fe film with Bs=1T, it ispossible to use a microcrystalline sputter film such as Fe—Ta—N film,Fe—Ta—N film, and Fe—Ta—C film with Bs=1.4 to 1.6T, or an amorphoussputter film such as Co—Zr film, Co—Ta—Zr film, and Co—Nb—Zr film withBs=1 to 1.6T. Naturally, the material for the upper magnetic pole frontend layer and the lower magnetic pole front end portion may be used.

[0134] To increase the recording magnetic field intensity, a magneticmaterial having a saturation magnetic flux density at least equal to orhigher than that of the lower magnetic pole main layer or the uppermagnetic pole top layer is used for the upper magnetic pole front endlayer and the lower magnetic pole front end portion which arerespectively opposite to the recording gap. There may be provided amulti-layered construction so that a high Bs film is used for a portionof one of the lower magnetic pole front end portion and the uppermagnetic pole front end layer adjacent to the recording gap or portionsof both the lower magnetic pole front end portion and the upper magneticpole front end layer adjacent to the recording gap, and a lower Bs filmis used for a layer on the opposite side of the recording gap.

[0135] The magnetic material for use in the upper magnetic pole toplayer and the lower magnetic pole main layer may have a saturationmagnetic flux density lower than that of the magnetic material for usein the upper magnetic pole front end layer and the lower magnetic polefront end portion. To reduce eddy current to enhance the high frequencyrecording characteristics, the specific resistance is preferably high.For example, the CoNiFe film for use in the upper magnetic pole frontend layer and the lower magnetic pole front end portion in theembodiments of the present invention has a specific resistance of 17 to20 μΩcm. The 46Ni—Fe film for use in the upper magnetic pole top layerand the lower magnetic pole main layer has a high specific resistance of45 to 55 μΩcm. The high specific resistance can reduce the eddy currentof the upper magnetic pole top layer and the lower magnetic pole mainlayer which are large and susceptible to the eddy current effect, andincrease the rising rate of the magnetic field at a high frequency so asto enhance the high-frequency recording characteristics. The magneticmaterial for use in the upper magnetic pole top layer and the lowermagnetic pole main layer desirably has a specific resistance of 45 μΩcmor more.

[0136] In the thin film head of the present invention, when the lowermagnetic pole front end portion and the lower magnetic pole rear endportion are formed on the lower magnetic pole main layer, basically, aphotoresist is coated onto the lower magnetic pole, which is thenexposed using a mask of a shape to be the lower magnetic pole front endportion and the lower magnetic pole rear end portion. Then, the resistof a shape to be the lower magnetic pole front end portion and the lowermagnetic pole rear end portion is removed by development. Thereafter,the magnetic material to be the lower magnetic pole front end portionand the lower magnetic pole rear end portion is formed by a platingmethod; that is, it is produced by a so-called frame plating method. Theshape of the lower magnetic pole front end portion can be producedaccurately.

[0137] On the other hand, there is a method in which after the lowermagnetic pole main layer is formed, the portion to be the lower magneticpole front end portion is protected by a resist so as to engrave thecoil portion in by ion milling. As in the present invention, to form thelower magnetic pole front end portion having a height of 0.3 to 2 μm, ittakes long time for milling and the milled material is re-deposited ontoother portions. Thus, this method is not used in the present invention.In the present invention, the surface for defining a gap depth of thelower magnetic pole front end portion formed by the flame plating methodis formed almost perpendicular to the recording gap surface within anerror of about ±10°.

[0138] In the present invention, the lower magnetic pole front endportion and the lower magnetic pole rear end portion can be producedseparately using another kind of magnetic material. Basically, in viewof reducing the producing process, the lower magnetic pole front endportion and the lower magnetic pole rear end portion are produced at thesame time using the same kind of magnetic material.

[0139] The effect of enhancing the track width accuracy and ofincreasing the magnetic field in the thin film head of the presentinvention can be obtained in any track width. In particular, the thinfilm head of the present invention can exhibit an excellent effect in aregion of the small track width of 0.4 μm or less in which reduction ofthe magnetic field intensity and the track width accuracy will be a mainproblem. In addition, the thin film head of the present invention canexhibit an excellent effect when incorporated into a magnetic diskapparatus using a high-coercivity recording medium of 3500 Oe or more.Further, the thin film head of the present invention can exhibit anexcellent effect in a magnetic disk array apparatus incorporating amagnetic disk apparatus using the thin film head of the presentinvention.

[0140] As described above, in the thin film head of the presentinvention, the lower magnetic pole front end portion is provided on thelower magnetic pole main layer to suitably select the shape dimensionsof the respective parts of the head are selected suitably. It ispossible to provide a thin film head having a high track width accuracyand a high recording magnetic field intensity. The projection stepportion having a width larger than that of the upper magnetic pole frontend layer is provided on the lower magnetic pole front end portion. Itis possible to reduce the unnecessary medium in-plane magnetic field inthe off-track position. The magnetic disk apparatus and the magneticdisk array apparatus equipped with the thin film head of the presentinvention are combined with a medium having a coercivity of 279kA/m(3500 Oe) or more. It is possible to realize the disk magnetic apparatusand the magnetic disk array apparatus having excellent performance.

What is claimed is:
 1. A thin film head comprising in combination: areading part consisting of a magnetic shield layer and a reading elementformed on a substrate; and a recording part consisting of a lowermagnetic pole, an upper magnetic pole, coils, and a non-magneticinsulating layer; wherein said lower magnetic pole consists of a lowermagnetic pole main layer, a lower magnetic pole front end portion, and alower magnetic pole rear end portion; said upper magnetic pole has itsfront end portion opposite to the lower magnetic pole front end portionthrough a recording gap layer and its rear end portion connectedmagnetically to the lower magnetic pole rear end portion; said coils aredisposed between the lower magnetic pole main layer and the uppermagnetic pole; said non-magnetic insulating layer is filled among thecoils, the lower magnetic pole main layer and the upper magnetic pole;the lower magnetic pole front end portion has a width in the track widthdirection smaller than the width of the lower magnetic pole main layerand has, at the upper magnetic pole side, a projection step portionhaving a width in a floating surface almost equal to the track width;the upper magnetic pole consists of an upper magnetic pole front endlayer, an upper magnetic pole rear end layer, and an upper magnetic poletop layer; and a surface for defining a gap depth of said lower magneticpole front end portion is formed almost perpendicular to the recordinggap surface, so that the height of said lower magnetic pole front endportion in the medium running direction is 0.3 μm to 2 μm.
 2. The thinfilm head according to claim 1, wherein the width of the lower magneticpole front end portion in the track width direction is 1 μm to 30 μm. 3.The thin film head according to claim 1 or 2, wherein the surface otherthan the projection step portion of said lower magnetic pole front endportion at the upper magnetic pole side is inclined at, at least oneinclination angle to the recording gap surface.
 4. A thin film headcomprising in combination: a reading part consisting of a magneticshield layer and a reading element formed on a substrate; and arecording part consisting of a lower magnetic pole, an upper magneticpole, coils, and a non-magnetic insulating layer; wherein said lowermagnetic pole consists of a lower magnetic pole main layer, a lowermagnetic pole front end portion, and a lower magnetic pole rear endportion; said upper magnetic pole has its front end portion opposite tothe lower magnetic pole front end portion through a recording gap layerand its rear end portion connected magnetically to the lower magneticpole rear end portion; said coils are disposed between the lowermagnetic pole main layer and the upper magnetic pole; said non-magneticinsulating layer is filled among the coils, the lower magnetic pole mainlayer and the upper magnetic pole; the lower magnetic pole front endportion has a width in the track width direction smaller than the widthof the lower magnetic pole main layer and has, at the upper magneticpole side, a projection step portion having a width in a floatingsurface almost equal to the track width and having a width in theposition away from the floating surface in the head rear portiondirection larger than the width of the upper magnetic pole; and asurface for defining a recording gap depth of said lower magnetic polefront end portion is formed almost perpendicular to the recording gapsurface.
 5. The thin film head according to any one of claims 1 to 4,wherein said upper magnetic pole front end layer has a widthcorresponding to the track width from the floating surface to themagnetic pole expansion position, so as to increase the width from themagnetic pole expansion position to the head rear portion direction. 6.The thin film head according to any one of claims 1 to 5, wherein saidupper magnetic pole front end layer consists of a plurality of magneticlayers having different saturation magnetic flux densities, so that themagnetic layer of the recording gap side has a saturation magnetic fluxdensity higher than that of the magnetic layer at a side farther fromthe recording gap.
 7. The thin film head according to any one of claims1 to 6, wherein the saturation magnetic flux density of at least somemagnetic materials for use in said upper magnetic pole front end layeror the lower magnetic pole front end portion is higher than that of themagnetic material for use in the lower magnetic pole main layer and theupper magnetic pole top layer.
 8. The thin film head according to anyone of claims 1 to 7, wherein the specific resistance of the magneticmaterial for use in the lower magnetic pole main layer or the uppermagnetic pole top layer is higher than that of the magnetic material foruse in the upper magnetic pole front end layer or the lower magneticpole front end portion.
 9. A producing method of the thin film headaccording to any one of claims 1 to 8, wherein the lower magnetic polefront end portion is produced on the lower magnetic pole main layer by aflame plating method.
 10. A magnetic disk apparatus comprising: amagnetic recording medium; a motor for driving the same; a magnetic headfor recording and reading onto the magnetic recording medium; amechanism for positioning the magnetic head, a circuit system forcontrolling these; and a circuit system for supplying a recording signalto the magnetic head and processing a reading signal from the magnetichead; wherein at least the one thin film head according to any one ofclaims 1 to 9 is mounted as the magnetic head, and said magneticrecording medium has a coercivity of 279kA/m (3500 Oe) or more.